Max/zknym docs

[mfahampshire]

Initial docs for zknyms

• [x] docs pages: overview
• [x] diagrams: in-line or link to
• [x] ~~(once decided upon naming) change 'tickets' and 'ticketbook' in nym-cli commands <== checking into how much this needs to touch as we use 'tickets' all over, checking if I can just change stuff in commands/ and tools/nym-cli and whether that pulls in e.g. logging from elsewhere.. NB generate-ticket() is in carmello branch, would need to pull in from here. Other changes are currently uncommited in the ecash-docs branch. NBB there is more to pull in as well in this bracnh https://github.com/nymtech/nym/pull/4827/files#diff-397393b23836f0071b8f52282ce73342a8812a55704dae034a06f93bb37cd53f~~ split it out and in here: https://github.com/nymtech/nym/tree/max/update-nym-cli-terminology
• [x] ~~replace command output in docs with new~~
• [x] remove final TODOs from info admonishments regarding ^
• [x] ~~rebase~~

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